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Reduce allocations.

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Bert Peters
2019-12-16 13:14:29 +01:00
parent 596e8ccde3
commit 77cb308287
1 changed files with 6 additions and 7 deletions
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13
2019/src/day16.cpp
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@@ -36,9 +36,8 @@ namespace {
return partial_sums; return partial_sums;
} }
std::vector<int> advance(const std::vector<int>& numbers) { void next_phase(const std::vector<int>& numbers, std::vector<int> &new_numbers) {
std::vector<int> new_numbers; new_numbers.resize(numbers.size());
new_numbers.reserve(numbers.size());
for (int rank = 0; rank < numbers.size(); ++rank) { for (int rank = 0; rank < numbers.size(); ++rank) {
auto partial_sums = partial_sum(numbers); auto partial_sums = partial_sum(numbers);
@@ -52,18 +51,18 @@ namespace {
n = std::abs(n % 10); n = std::abs(n % 10);
new_numbers.push_back(n); new_numbers[rank] = n;
} }
return new_numbers;
} }
} }
void aoc2019::day16_part1(std::istream &input, std::ostream &output) { void aoc2019::day16_part1(std::istream &input, std::ostream &output) {
auto numbers = read_input(input); auto numbers = read_input(input);
auto new_numbers = numbers;
for (int i = 0; i < 100; ++i) { for (int i = 0; i < 100; ++i) {
numbers = advance(numbers); next_phase(numbers, new_numbers);
std::swap(numbers, new_numbers);
} }
std::copy(numbers.begin(), numbers.begin() + 8, std::ostream_iterator<int>(output)); std::copy(numbers.begin(), numbers.begin() + 8, std::ostream_iterator<int>(output));